1. Field of the Invention
The present invention relates to a cooling device for a battery pack including a plurality of prismatic rechargeable batteries arranged in parallel and to such a rechargeable battery.
2. Description of Related Art
In a conventional battery pack, in order to prevent decrease in a battery output, charging/discharging efficiency, and battery service life due to the elevation of the battery temperature by heat generation that occurs along with charging/discharging, for example, Japanese Patent Laid-Open Publication No. 2001-167803 discloses a fan provided to upwardly send cooling air between cells included in the battery pack or between battery modules, each including a plurality of serially connected cells.
An example of this type of cooling device for a battery pack will be described with reference to FIGS. 9 and 10. In FIG. 9, the reference numeral 51 denotes a battery pack serving as a driving power source for electric vehicles including hybrid cars. The battery pack 51 includes ten to thirty rechargeable batteries 52 that are arranged in parallel with ventilation spaces 54 being provided in a vertical direction between the rechargeable batteries 52. The rechargeable batteries 52 are interposed between a pair of end plates 55 provided on both ends in a parallel direction with a binding band 56. The rechargeable batteries 52 are integrally fixed in this manner to constitute the battery pack 51.
As shown in FIG. 10, each of the rechargeable batteries 52 is constituted as a battery module including a plurality of cells 53 that are arranged in parallel in an integrated manner and connected in series. Each of the cells 53 is constituted by housing an electrode plate group and an electrolyte solution in a battery case. Connection terminals 57 provided on both ends of the rechargeable batteries 52 in a protruding manner are sequentially connected in series so as to obtain a predetermined output voltage of the battery pack 51. Moreover, on both side walls 58 of the rechargeable battery 52, longitudinal ribs 59 are provided between the cells 53 and on both ends of the rechargeable battery 52. When the rechargeable batteries 52 are arranged in parallel so that the both side walls 58 are opposed to each other, the longitudinal ribs 59 abut on each other to form the ventilation spaces 54 between both side walls 58.
The under face of the battery pack 51 is covered with a lower hood 61 with an air blowing space 60 being provided therebetween, whereas the upper face of the battery pack 51 is covered with an upper hood 63 with an air exhausting space 62 being provided therebetween. An air duct 66 extending from a blower fan 65 is connected to an air inlet port 64 provided on one end of the lower hood 61, whereas an air exhausting duct 68 is connected to an air exhausting port 67 provided on one end of the upper hood 63.
In the above-described cooling device for a battery pack, air in a vehicle compartment is sent by the blower fan 65 to the air blowing space 60 below the battery pack 51. In this manner, cooling air flows upwardly from below through the ventilation spaces 54 between the rechargeable batteries 52 to be exhausted into the air exhausting space 62, thereby allowing each of the rechargeable batteries 52 included in the battery pack 51 to be cooled. However, for such cooling, a space is required for forming the air blowing space 60 and the air exhausting space 62 below and above the battery pack 51. Since a large space is necessitated in a vertical direction for placing the battery pack 51, the position where the battery pack 51 is placed is restrained in a case where the battery pack 51 is to be used as a driving power source for vehicles.
In order to ensure a space for placing the driving power source for vehicles therein without any difficulty to increase the degree of freedom for a layout, a height of the battery pack 51 including the cooling device must be reduced.